45771405-Đồ-an-tốt-nghiệp-Vũ-Huy-Cường

7/31/2019 45771405--an-tt-nghip-V-Huy-Cng

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nh gi thng lng ca cc giao thc nh tuyn trong mng Ad hoc

LI NI U

Cng vi s gia tng nhanh chng v s lng cng nh cng ngh ca cc thit

b di ng ko theo nhu cu ca ngi s dng cng ngh khng dy ngy cng cao v

a dng.V vy p ng c xu th , mng thng tin khng dy ngy nay phignh vc trng trch ln hn l gii quyt vn v lu lng a phng tin, tc

cao,cht lng ngy cng phi tt hn.

Song song vi yu cu h tr a phng tin vi cht lng dch v (QoS) m

bo, cc cng ngh giao tip khng dy khc nhau xut hin,Ad hoc l mt kiu

mng thng tin khng dy linh hot. l tp hp ca hai hay nhiu thit b c trang

b kh nng ni mng v truyn thng khng dy.Cc thit b c th giao tip vi

cc nt mng khc ngay lp tc trong vng ph sng hay mt thit b khng dy khcngoi bn ngoi vi iu kin c cc nt trung gian chuyn tip thng tin t nt

ngun n nt ch.Ad hoc c kh nng t t chc v thch nghi, khi hnh thnh c

th b gii tn bt c lc no m khng cn n bt c s qun tr h thng no.Ad hoc

c nhiu dng khc nhau v c th di chuyn,ng c lp hay ni mng.Cc nt mng

c th pht hin s c mt ca cc thit b khc trong gii v tuyn v thc hin s bt

tay cn thit cho php truyn thng, chia s thng tin v dch v.Tp ca mng

thng tin ty bin thay i ng do cc thit b khng b rng buc vo mt v tr c th

nn vic truy nhp phng tin tp trung. Giao thc nh tuyn phi gim lu lng

iu khin, n gin tnh ton ng nh tuyn. Chnh v th giao thc nh tuyn

ng vai tr quan trng trong vn hnh mng Ad hoc.

n l tng quan v bn giao thc nh tuyn trong mng Ad hoc, nh gi

thng lng ca cc giao thc da trn cng m phng OMNET++. Do thi gian

cng nh trnh cn hn ch, n khng trnh khi nhng thiu st, em rt mong

nhn c kin ng gp.

c th hon thnh c n tt nghip ny, em c hc hinhng kin

thc qu bu t cc thy, c gio ca Trng i hc Bch Khoa H Ni trong sut

V Huy Cng- T3- K49 1


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nm nm i hc. Em v cng bit n s dy d, ch bo tn tnh ca cc thy, cc c

trong thi gian hc tp ny.

Em xin by t lng bit n ca mnh ti thy Nguyn Trung Dng B mn H

thng vin thng Khoa in t vin thng Trng i hc Bch Khoa H Ni,

ngi nh hng cho nhng nghin cu ca em, ngi trc tip hng dn v ch

bo em hon thnh n ny.

Cui cng, em xin cm n gia nh, bn b lun to iu kin thun li, ng

vin v gip em trong sut thi gian hc tp v nghin cu n. Ngoi ra, kin

thc thu c t cc thy c cng l ngun c v tinh thn ln nht gip em c th tp

trung v hon thnh tt ti tt nghip ny.

H Ni, thng 5- 2009

Sinh vin

V Huy Cng



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TM TT N

Mng Ad hoc l mt cng ngh hu dng trong mng khng dy. Cng ngh ny

cho php cc nt mng giao tip trc tip vi nhau bng cch s dng my thu pht v

tuyn m khng cn c c s h tng c nh. y l mt c trng ring ca mng Adhoc so vi cc mng truyn thng trc y nh mng cellular hay mng LAN khng

dy khi cc nt giao tip vi nhau thng qua trm gc (Base Station). Tuy nhin,

mang Ad hoc phi i mt vi mt s thch thc nh gii hn phm vi truyn dn, vn

trm n, mt gi do li ng truyn, s chuyn ng ca cc nt mng lm thay

i tuyn ng, s rng buc v bng thng v nng lng. Giao thc nh tuyn

c s dng Khm ph tuyn gia cc nt gip cho vic giao tip trong mng d

dng hn. Mc ch chnh ca mt giao thc nh tuyn trong mng Ad hoc l thit lptuyn ng chnh xc v hiu qu gia cc cp nt. n a ra tng quan v bn

giao thc nh tuyn: DYMO, DSR, AODV, OLSR, s dng cng c m phng

OMNET++ v nh gi tr u cui ca cc giao thc ny da trn cc thng s t ra.

n gm 5 chng

Chng 1: Tng quan v mng Ad hoc

Chng 2: nh tuyn trong mng Ad hoc

Chng 3: Thng s nh gi v m hnh chuyn ng trong m phng mng

Ad hoc

Chng 4: M phng v nh gi thng lng ca OLSR, AODV, DSR v

DYMO bng OMNET++

Chng 5: Kt lun



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ABSTRACT

Ad hoc networks are the ultimate frontier in wireless communication. Thistechnology allows network nodes to communicate directly to each other using wireless

transceivers without the need for a fixed infrastructure. This is a very distinguishing

feature of ad hoc networks with respect to more traditional wireless networks, such as

cellular networks and wireless LAN, in which nodes communicate with each other

through BS. Some challenges that ad hoc networking faces are limited wireless

transmission range, hidden terminal problems, packet losses due to transmission errors,

mobility- induced route changes, bandwidth and battery constraints. In order tofacilitate communication within the network, a routing protocol is used to discover

routes between nodes. The primary goal of such an Ad hoc network routing protocol is

correct and efficient route establishment between a pair of nodes so that message may

be delivered in a timely manner. This thesis provides an overview of four different

routing protocols: DYMO, DSR, AODV, OLSR, uses OMNET++ simulator and

evaluates throughput of these protocols based on a given set of parameters.

The thesis has a total of 5 chapters:

Chapter 1: Overview of Ad hoc network

Chapter 2: Routing in Ad hoc network

Chapter 3: Protocol Evaluation parameters and Mobility models

for Ad hoc network simulation

Chapter 4: Simulating and evaluating throughput of AODV,

OLSR, DSR and DYMO in OMNET++

Chapter 5: Summary



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MC LC

LI NI U..................................................................................................1

TM TT N............................................................................................3

ABSTRACT......................................................................................................4

MC LC........................................................................................................5

DANH SCH HNH V...................................................................................6

DANH SCH BNG BIU..............................................................................7

1 CHNG 1. TNG QUAN V AD HOC NETWORK ......................................7

CHNG 2. NH TUYN TRONG MNG AD HOC ......................................18

3 CHNG 3 THNG S NH GI V M HNH CHUYN NG

TRONG M PHNG MNG AD HOC ..................................................................44

4 CHNG 4. M PHNG V NH GI THNG LNG CA AODV,

OLSR, DSR V DYMO BNG OMNET++ ............................................................51

5 CHNG 5. KT LUN .......................................................................................69

TI LIU THAM KHO................................................................................70

BNG THUT NG VIT TT.....................................................................72

PH LC......................................................................................................73



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DANH SCH HNH V

Hnh 1.1 M hnh m t khi nim mng Ad hoc.....................................................9

Hnh 1.2 ng dng cho cc dch v khn cp khi c thin tai...............................11

Hnh 1.3 ng dng trong cc hi ngh.....................................................................12

Hnh 1.4 ng dng cho home networking...............................................................12

Hnh 1.5 ng dng cho mng c nhn.....................................................................13

Hnh 1.6 ng dng cho mng xe c..........................................................................14

Hnh 2.1 H ta c bn m t mi trng mng Ad Hoc.................................21

Hnh 2.2 Phn loi cc giao thc nh tuyn trong mng Ad hoc..........................24

Hnh 2.3 Qu trnh pht trn lan bn tin qung b................................................28

Hnh 2.4 Bu chn MPR...........................................................................................29

Hnh 2.5 Khm ph tuyn trong DSR.......................................................................32

Hnh 2.6 Duy tr tuyn, nt C khng th chuyn tip t A n E qua .................34

lin kt ti bc nhy tip theo D ca n.................................................................34

Hnh 2.7 Thit lp tuyn ng i ngc................................................................38

Hnh 2. 8 Thit lp tuyn ng thun.....................................................................40

Hnh 2.9: S khc nhau gia AODV v DYMO......................................................42

Hnh 3.1 M hnh di chuyn Random Waypoint.....................................................49

Hnh 3.2 M hnh di chuyn hng ngu nhin.......................................................50

Hnh 4.1 Cc module n gin v kt hp...............................................................53

54

Hnh 4.2 Cc kt ni..................................................................................................54

Hnh 4.4 Qu trnh gi bn tin RREQ ca DYMO.................................................62

63Hnh 4.5 Qu trnh gi bn tin RREP ca DYMO..................................................63

64

Hnh 4.6 Qu trnh gi gi tin d liu ca DYMO..................................................64

65



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Hnh 4.7 Qu trnh gi ACK bo nhn ca DYMO................................................65

Hnh 4.9 Thng lng u cui - u cui.............................................................67

Qua biu thng lng < hnh 4.9 > ta nhn thy thng lng t l thun vi gi

nhn.............................................................................................................................67Thng lng ca DYMO l cao nht do DYMO l giao thc nh tuyn hot ng

theo yu cu hoc theo bng iu khin,l s ti u ca DSR v AODV.Khi cc

nt mng chuyn ng lin tc,thng lng ca DYMO vn rt cao ...................67

Thng lng ca OLSR cao hn AODV v DSR v OLSR c th p ng khi topo

mng thay i, n cho php khm ph tuyn nhanh chng ti cc hng xm v

cc MPR ca chng thit lp kt ni vi cc nt khc.......................................67

Khi mc di chuyn tng (gim pausetime) th thng lng ca 3 giao thcDSR, AODV, OLSR gim r rt vi mc gim tng ng nhau.Trong khi

th DYMO th hin c s n nh ca mnh khi c thng lng kh cao.OLSR

c thng lng cao hn AODV v DSR....................................................................67

DANH SCH BNG BIUBng 3.1 Bng cc bin trong thng s di chuyn....................................................47

Bng 4.1 Bng thng s nh gi dng trong m phng........................................66

1 CHNG 1. TNG QUAN V AD HOC

NETWORK



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Chng ny trnh by cc khi nim tng quan nht v mng Ad hoc, cc ng

dng trong nhiu lnh vc cuc sng ca mng Ad hoc. ng thi, cp n cc

thch thc m mng Ad hoc ang phi i mt.

1.1 M U

Mng my tnh t lu tr thnh mt phn khng th thiu i vi nhiu lnh

vc i sng x hi, t cc h thng mng cc b n h thng mng ton cu nh

Internet. Mng my tnh a mi ngi trn th gii n gn nhau hn, mi ngi

c tip cn vi mt ngun thng tin, tri thc phong ph.

X hi pht trin, con ngi vn ng khng ngng, mt ngi kt ni vo mng

bng cp vt l th vic di chuyn ca h b hn ch, nhu cu t ra l va kt ni va

c th di chuyn v c th kt ni bt c u mt cch n gin. Chnh nhu cu ny

kch thch ngnh cng nghip mng khng dy tim nng pht trin mnh m.

Mng Ad hoc l mt kiu mng khng dy rt linh hot. l tp hp ca hai

hay nhiu thit b c trang b kh nng ni mng v truyn thng khng dy. Cc

thit b nh vy c th giao tip vi tt c thit b mng khc ngay lp tc trong di v

tuyn (vng ph sng, phm vi m thit b mng nhn bit c) hay mt thit b v

tuyn khc nm ngoi di v tuyn ca chng vi iu kin c cc node trung gian

chuyn tip thng tin t node ngun n node ch. Thit b h tr mng Ad hoc a

dng v s dng kh ph bin nh laptop, in thoi di ng Internet. V c nhiu u

th vt tri v nhng thch thc cn gii quyt, ngy nay mng Ad hoc v ang

c nghin cu trin khai thnh cng mt s nc m ph bin l M. Mng Ad

hoc c bit hu ch trong cc ng dng nh khc phc thm ha thin nhin, quc

phng, y t, hi ngh nn c xu hng ng dng rng ri trn th gii.

1.2 KHI NIM

Mng Ad hoc l t hp ca cc node di ng c kt ni vi nhau bng cc lin

kt khng dy, cc node t do di chuyn nn kin trc mng c th thay i lin tc m



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khng d on c. Mi node mng c mt giao din v tuyn giao tip vi cc node

mng khc thng qua sng v tuyn hoc hng ngoi. Cc mng ny khng dng bt

c s h tr c s h tng mng c nh hay chu s qun l tp trung no. y l mt

c im ring bit ca mng Ad hoc so vi cc mng khng dy truyn thng mngchia , mng WLAN, trong cc node (cc thu bao di ng ) lin lc vi nhau thng

qua trm v tuyn c s.

Hnh 1.1 M hnh m t khi nim mng Ad hoc

Trong Ad hoc khng tn ti khi nim qun l tp trung, n m bo mng s

khng b sp v trng hp nt mng di chuyn ra ngoi khong truyn dn ca cc nt

mng khc. Nt mng c th ra vo bt c lc no. Do khong truyn dn ca n t

mng l hn ch nn chng trao i thng tin bng phng php truyn gi tin qua

nhiu bc (Multihops). lm c iu ny, th tt c cc nt mng phi c kh

nng chuyn tip gi tin n nt mng khc, do vy tt c cc nt mng trong Ad hoc

c th hot ng nh my trm v router. Nn nt mng c th bao gm mt router v

mt my trm lin kt vi nhau. Mt router thc hin cc giao thc nh tuyn, my

trm di ng c a ch IP.



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Ad hoc cng c kh nng thc hin thay i v cu hnh mng v khc phc s c

ca nt mng thng qua th tc cu hnh li mng. V d: Nu nt mng ri khi mng

s gy ra s c lin kt, nt mng b nh hng c th yu cu ng nh tuyn mi

v vn s c gii quyt. iu ny s gy ra tr trn mng, tuy nhin vi ngi sdng Ad hoc vn hot ng bnh thng.

Ad hoc c nhiu u im ca mng truyn thng v tuyn thng thng, lin kt

gia cc nt mng c hnh thnh ngay khi chng nm trong khong truyn dn ca

nhau

1.3 C IM

Ad hoc thng c m t c cu trc mng thay i do s thay i v tr ca cc

nt mng. Cc giao thc nh tuyn c c ch t pht hin cc thay i v nh tuyn

thng qua cc thut ton nh tuyn thng thng nh vector khong cch v trng thi

cc lin kt. Mt c im khc ca cc nt mng trong mng Ad hoc: b gii hn v

kh nng ca CPU, b nh, dung lng pin v bng thng. Khi nng lng s dng b

gii hn ko theo gii hn v kh nng truyn dn. Thit b truy nhp, mi trng v

tuyn cng c cc c im c bit m ngi thit k cn lu tm khi a ra cc giao

thc nh tuyn cho Ad hoc. V d: cc lin kt mt chiu, n xut hin trong trng

hp 2 nt mng c cng sut pht khc nhau nn c khong truyn dn khc nhau, ch

cho php mt nt mng nghe nt mng kia. Lin kt mt chiu ch c trong Ad hoc,

khng tn ti trong mng t bo. S dng phng php nh tuyn nhiu bc th cc

nt mng c th tit kim c nng lng pht ra.

1.4 NG DNG

Ad hoc c ng dng cho hi tho, ng dng trong qun s. N cng c s

dng cho trng hp trin khai c s h tng mng l kh khn. V d: khch hng c

th chia s t p tin d liu sn bay, sinh vin trao i thng tin vi nhau trong tit



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hc Khi my tnh di ng giao tip thng qua giao din mng LAN v tuyn, th

nhm cc my tnh hnh thnh mng Ad hoc, khi my tnh c th truy nh p

Internet, ti nguyn trn mng nh my in, my scan...

1.4.1 Dich v khn cp

Bt k u khi c trng hp khn cp xy ra u cn c s kt hp ca cc nhn

vin cu h. Gii php thng thng l dng thit b v tuyn. Tuy nhin, khi c s h

tng b hng hoc khng cn hot ng th gii php l g? Ad hoc chnh l cu tr li

nhanh nht v ph hp nht. iu ny c th khng c ngha vi khu vc tn tht

nh, tuy nhin vi thm ha thin nhin c khu vc nh hng tn ph rng ln, vic

lin lc rt quan trng nn Ad hoc tr thnh gii php hu ch.

Hnh 1.2 ng dng cho cc dch v khn cp khi c thin tai

1.2.2 Hi ngh

Trong hi ngh, hi tho cn trao i thng tin gia cc i biu hoc vi hi ngh

khc. y l mt nhu cu ln trong thi i pht trin nhanh v thng tin nh hin nay,

khi m gii php homenetwork cha tht s sn sng. Gii php hin ti l s dng cc



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mng c sn cho cc i biu tham d tuy nhin n c tr l n, v d gii php

Mobile IP .V Ad hoc l gii php chim u th.

Hnh 1.3 ng dng trong cc hi ngh

1.2.3 Home NetworkingR rng s hin din ca my tnh xch tay v ng dng khng dy lm nhu cu

v home network tng cao.Vic s dng k thut ca Ad hoc cho php chng t cu

hnh v hnh thnh mng, iu ny tin li cho c ngi khng tht s am hiu v

mng cng nh gim c chi ph cho xy dng thit k mng. Hn na, nu ta c

nhu cu s dng my tnh cng s, trng hc th khi lng thng tin qun l mng

gim xung r rt.

Hnh 1.4 ng dng cho home networking

1.2.4 Mang c nhn (PAN)



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thi i thng tin th 1 ngi cn mang theo nhiu cng c h tr cho cng vic

(in thoi,Palm...) khi chng c lin kt vi nhau hnh thnh mng c nhn PAN th

r rng mang li nhiu tin ch hn cho ngi s dng. PAN l mng di ng do con

ngi khng th ngi yn mt ch, tuy nhin khi kt ni vi mng PAN khc cn trgip ca Ad hoc.

Hnh 1.5 ng dung cho mang c nhn

1.2.5 H thng nhung (embeded system)

Ngy cng c nhiu my mc cn kt ni vi nhng vt xung quanh ko theo nhu

cu ca Ad hoc. N c th l chi c kh nng k t ni mng, tng tc c vi

home network tm kim d liu trn internet hoc c th kt ni vi in thoi, c

th iu chnh volume ca TV khi c cuc gi n....p ng nhiu nhu cu ca ngi

s dng.

1.2.6 Mang xe c (vehicular network)

VANET (Vehicular Ad Hoc Network) gi l mng xe c Ad hoc, l h thng

mng khng cn c s h tng, c to thnh t cc phng tin xe c lu thng trn

ng. Chng c trang b thit b thu pht c th lin lc, chia s v trao i



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thng tin vi nhau ging nh mt nt trong mng Ad hoc. Thng tin trao i trong

mng VANET bao gm thng tin v lu lng xe c, tnh trng kt xe, tai nn giao

thng, nguy him cn trnh v c nhng dch v thng thng nh dch v a phng

tin, Internet....

Hnh 1.6 ng dng cho mng xe c

1.2.7 Mang cm bin (sensor network)

Mng cm bin khng dy l mt ng dng in hnh ca Ad hoc. Hin nay c

nhng quan tm ng k cho s pht trin kiu mng ny,ch yu l trong qun s,

cng an, tnh bo, kho c hc, nghin cu a l....Cc b cm bin c th c kch

thc nh nhng kh nng truyn thng v lu tr tng i tt. Trong qun s

dng nhng my mc hin i nhng kch c gn nh ht bi nn i phng rt kh

pht hin v ph hy chng.

Trong lnh vc y t, cc b cm bin cho php gim st lin tc thng tin tiu

chun v s sng. Trong cng ngh thc phm, k thut nhp cm bin c p dng

gim st cht lng c th gip ngn nga cc sn phm khng t yu cu nn tng

mc tha mn cho khch hng. Trong nng nghip, cc b cm bin c th gip xc

nh cht lng t trng v m, chng cng c th pht hin cc hp cht khc.



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Ngoi ra, cc b cm bin cng c s dng rng ri trong thng tin thi tit v mi

trng.

1.3 NHNG THCH THC I VI MNG AD HOC

1.3.2 Chi ph cho vic sdng tn s

Hu ht cc mng Ad hoc th nghim hin nay u da trn bng tn ISM.

ngn nga nhiu, mng Ad ho phi hot ng qua mt s di ph c th no , c

cp pht. Ph tn khng ch c cp pht v gim st cht ch m cn cn phi c

tr ph.

1.3.3 C ch truy nh p

Khng ging nh mng t bo, trong mng Ad hoc khng c s iu khin t p

trung v ng b ton cc. Do cc phng php a truy nh p truyn thng nh

TDMA v FDMA khng cn thch hp na. Ngoi ra, nhiu giao thc iu khin truy

nh p phng tin MAC (Media Access Control) cng khng gii quyt c s di

ng ca nt mng. Do vy, cc k thut l p lch trnh v nh thi h tr QoS g p

nhiu kh khn.

Trong mng Ad hoc, do cng mt phng tin truyn thng c chia s bi

nhiu bn tham gia nn th tc truy nh p n knh chung phi c thc hin theo

kiu phn b nh s h tr ca giao thc MAC. Giao thc MAC phi tnh n truy

nh p knh trong khi ng thi phi trnh c s xung t vi cc nt ln cn. Do vy,

khi tnh ton thit k cc giao thc MAC cho mng Ad hoc phi tnh n kh nng di

chuyn, vn u cui n v cc vn lin quan khc.

1.3.4 inh tuyn v chuyn tip goi tin trong MANET



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c tnh ng ca mng Ad hoc gy ra s thay i thng xuyn v kh on

trc ca topo mng, lm tng kh v phc tp nh tuyn gia cc nt di

ng. Nhiu giao thc v thut ton nh tuyn c xut cho mng Ad hoc, tuy

nhin mi giao thc li c mt hn ch ring. Do vy, nghin cu v cc giao thc nhtuyn trong Ad hoc l mt vn rt quan trng.

1.3.5 Hiu qus dng ngun nui

Hu ht cc giao thc trong mng hin nay khng quan tm n tiu tn nng

lng ngun nui v cc my ch v cc b tnh tuyn thng c gi nh l tnh v

c cp ngun t ngun in chnh. Tuy nhin, cc thit b d ng hu ht c cp

ngun t ngun nui c l p.K thut ngun nui vn thng i chm hn so vi kthut vi x l. Thi gian cp ngun ca pin loi tt nh Li-ionh hin nay cng ch ti

a t 2 n 3 gi (hin nay c mt s laptop c thi gian s dng ln n 8h, tuy

nhin gi thnh vn cn kh cao). S gii hn thi gian hot ng nh th ni ln tnh

cn thit phi bo tn tt ngun nui. c bit, i vi mng Ad hoc, do cc thit b di

ng phi thc hin vai tr ca c h thng u cui (tng tc ngi dng khi thc

hin cc ng dng ngi dng) ln vai tr ca mt h thng trung gian (chuyn tip

gi tin) nn s tiu tn nng lng ngun nui mt cch ng k, c bit l cc nttrung gian.

1.3.6 c tnh TCP

TCP (Transmission Control Protocol) l mt giao thc cui-cui c thit k

phc v vic iu khin nghn v iu khin lung trong mng. TCP l mt giao thc

hng lin kt nn cn c mt giai on thit l p kt ni u tin cho vic truyn d

liu. Kt ni b loi b khi vic truyn d liu hon thnh. Vi internet hin nay, giaothc mng IP l phi kt ni nn cn c mt giao thc truyn dn hng kt ni ng tin

cy qua mt giao thc mng khng tin cy. Tuy nhin, TCP gi s rng cc nt trong

tuyn l tnh nn vic iu khin nghn v iu khin lung ch c thc hin cc

nt ngun v ch.



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TCP da vo vic o c thi gian ton trnh-RTT (Round Trip Time) v mc tn

tht gi kt lun l c nghn mch xy ra trong mng hay khng. TCP khng th

phn bit c s c mt ca tnh di ng v s nghn mng. Cc nt chuyn ng

trong mt kt ni c th gy tn tht gi v lm cho RTT di hn. Do vy, cn c mts ci tin bo m rng giao thc truyn dn thc hin tt m khng nh hng

n thng lng truyn thng cui-cui.

1.4.2 Cht lng dch v (QoS)

Kh nng cung cp QoS ca mt mng ph thuc vo cc c tnh bn trong ca

ton b cc thnh phn mng, t cc lin kt truyn pht n tng MAC v tng mng.

Cc kt ni khng dy c nng lc thp v hay thay i, t l li cao. Cc topo mng l

ng v c t l mt gi cao. Cc giao thc MAC da trn truy nh p ngu nhin khng

h tr QoS.

Cc giao thc MAC QoS gii quyt vn v xung t phng tin, h tr truyn

thng unicast tin cy, v cung cp vic d tr ti nguyn cho cc lu lng thi gian

thc trong mi trng khng dy phn tn. Rt nhiu cc giao thc MAC v cc ci

tin c xut cung cp vic m bo QoS cho lu lng thi gian thc trong

mi trng khng dy phn tn bao gm giao thc GAMA/PR v c ch xung t BB.

1.4.3 Tnh an ton v bo mt

Mi trng v tuyn trong mng Ad hoc l mi ngon bo b cho cc cuc tn

cng mo danh do c tnh qung b ca n. Cc giao thc nh tuyn trong mng Ad

hoc cn c h tr tnh nng xc thc, m ha nng cao tnh an ton, hiu nng ca

mng.

TNG KT

Chng ny trnh by nhng l thuyt tng quan mng Ad hoc. Trong mng

Ad hoc, topo mng thng xuyn thay i. Do vy, cc giao thc nh tuyn trong

mng Ad hoc cn gii quyt s di chuyn ca nt, rng buc nng lng,bng thng



18/79


2

CHNG 2. NH TUYN TRONG MNG AD HOC

c tnh ng ca Ad hoc gy ra s thay i thng xuyn v kh on trc ca

topo mng, lm tng kh v phc tp nh tuyn gia cc nt di ng. Nhiu

giao thc nh tuyn c a ra, tuy nhin, chng vn gp phi mt s hn ch nht

nh. Chng ny trnh by 4 loi giao thc trong mng Ad hoc: OLSR, AODV, DSR

v DYMO.

2.1 GIAO THC NH TUYN C IN



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Hin nay, cc giao thc nh tuyn a ra vi Ad hoc u da trn mt giao thc

nh tuyn c in lm thut ton c bn; do , vic tm hiu nghin cu cc hot

ng c bn ca cc giao thc ny l ht sc cn thit.

Giao thc c in nh: nh tuyn theo vector khong cch, nh tuyn theo trngthi lin kt c s dng t rt lu v tr nn rt quen thuc. Tuy nhin, cc

giao thc ny ch thch hp cho cu trc mng tnh, hot ng hiu qu mng Ad hoc

c tc di chuyn thp, cu trc mng t thay i. Ngoi ra, giao thc ny hot ng

ph thuc vo bn tin iu khin nh tuyn, nn vi s lng nt mng tng, yu cu

trao i gia cc nt mng tng ln, thng tin cp nht nh tuyn ln, chng s tiu

tn bng thng, nng lng v CPU. Bi v hai loi giao thc nh tuyn trn duy tr

nh tuyn n tt c cc nt mng, n khng quan tm nt mng c tham giao truyn

thng tin trong mng ti mi thi im hay khng. Hn na, giao thc nh tuyn c

in rng buc lin kt phi l hai chiu, nn cn c nhng ci thin nht nh cho

thng tin v tuyn ni chung v mng Ad hoc ni ring.

2.1.nh tuyn da trn trng thi lin kt

Phng php nh tuyn da trn trng thi lin kt da trn gi ca mi lin kt

(cost) v nt mng phi duy tr cu trc mng hon chnh vi tham s ny. Tham s

gi s c cp nht bng cch mi nt mng s gi thng tin qung b mt cch

lin tc gi ca cc lin kt xut pht t n ti tt c cc nt mng khc s dng

thut ton flooding. Mi nt mng khi nhn c cc thng tin ny s cp nht cu trc

mng v s dng thut ton tn ng i ngn nht chn nt mng tip theo cho

ng nh tuyn n nt mng khc. Lin kt c th c gi khng chnh xc do nhiu

nguyn nhn nh tr ng truyn, s phn tch ca mng... Cc cu hnh mng thay

i c th hnh thnh nh tuyn khp kn (loop), tuy nhin, ng nh tuyn kiu nyc thi gian tn ti ngn v chng s b xa ngay khi bn tin i qua ton b mng.

2.1.1. nh tuyn da trn vector khong cch



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Phng php ny nh tuyn da trn vector khong cch, c ci tin hn so vi

phng php nh tuyn da trn trng thi lin kt: mi nt mng ch gim st gi ca

lin kt xut pht t n, v khng qung b thng tin n tt c nt mng; n gi qung

b u n n nt lin cnh thng tin v khong cch ngn nht ti nt khc trongmng. Nt mng khc khi nhn c thng tin ny s tnh ton li bng nh tuyn

thng qua thut ton tm ng i ngn nht.

Giao thc ny hot ng hiu qu hn, n gin hn v yu cu t b nh lu tr

hn. Song, n c th sinh ra ng nh tuyn khp kn c thi gian tn ti thay i di

ngn khc nhau, v bng nh tuyn c th xy dng t thng tin tn ti lu qu trn

mng (khng c cp nht).

2.2 GIAO THC NH TUYN CHO MNG AD HOC

2.2.1 Cc yu cu chung

Do cc nt trong mng Ad Hoc lun di ng v c nhiu c tnh khc bit nn

khng th p dng cc giao thc nh tuyn thng thng. Cc mng Ad Hoc thng

c c trng bi mt topo ng do cc nt di chuyn lm thay i v tr vt l ca

chng. i vi mng Ad Hoc, giao thc nh tuyn ng t ra hiu qu v ph hp

hn cc phng php nh tuyn da trn vect khong cch v trng thi lin kt.

Thch thc trong vic thit k cc giao thc nh tuyn l kh nng cp nht c mc

di ng ca nt mng. Chch mc di ng ny l nguyn nhn lm thay i ton b

cu trc topo ca mng. Mt nt di ng thng b gii hn bi kh nng x l ca

CPU, dung lng lu tr, cng sut ngun v di thng.

Mi trng truy cp, mi trng v tuyn cng c nhng thuc tnh c bit cn

phi ch khi thit k cc giao thc cho mng Ad Hoc. V d cc ng truyn v

hng. Nhng ng truyn ny xut hin khi hai nt c cng khc nhau v cho

php ch mt nt nghe c nt kia. Nhng chng cng c th xut hin do nhiu t

mi trng xung quanh. a chng trong mi trng v tuyn c th gy ra tng ch

cng sut truyn v tng ch cng sut do mi quan h cn bc hai gia vng ph sng



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v cng sut pht ra. Bng cch s dng a chng, cc nt c th truyn cc gi tin i

s dng cng sut ra thp.

Hnh 2.1 M t cc trc c bn c th s dng c t mi trng mng Ad

Hoc. Trc u tin l s cc nt trong mng. Trc th hai l tc m ti topomng thay i. Trc th ba l ti lu lng trong mng. Khi mi trng di chuyn t

gc ca 3 trc, vn nh tuyn tr nn kh khn hn. Tng s nt, tng tc thay

i topo (ngha l tng tnh di ng ca nt), hoc tng ti lu lng mong mun trn

mng l thch thc i vi cc giao thc trong mng Ad Hoc.

Hnh 2.1 H ta c bn m t mi trng mng Ad Hoc

Yu cu i vi mt giao thc nh tuyn cho mng Ad hoc l g? Sau y l mt

s yu cu quan trng:

Hot ng phn tn: Giao thc nh tuyn trong mng Ad Hoc phi l giao thc

phn tn yu cu tin cy cao. Do cc nt l di ng nn giao thc nh tuyntp trung l khng ph hp. Mi nt mng phi thng minh to cc quyt

nh nh tuyn s dng cc nt ln cn.



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Khng lp vng: nng cao cht lng hot ng, giao thc nh tuyn cn

m bo ng nh c cung cp khng b lp vng, iu ny s lm gim

lng ph bng thng v cng sut tiu hao ca CPU.

S dng cc siu nt: Tt c cc giao thc hin c u gi nh rng cc nt di

ng l c cng cc c tnh da trn bn cht ca mng t t chc l tp hp

ca cc nt ngang hng. Mc d iu ny c th ng trong mt s trng hp,

tuy nhin, c trng hp m mng c cc nt c bng thng cao, ngun

nui n nh, lin kt khng dy tc cao hn so vi cc nt khc. Cc nt

nh vy c gi l cc siu nt. Cc mng t t chc trong trng hp ny

thng c cu trc 2 mc: vng backbone v vng ph. Vng backbone bao

gm cc siu nt. Thm vo cc siu nt thng c gi nh l c di

chuyn thp hn cc nt thng duy tr s n nh ca backbone. Cc nt

thng khng cn c quyt nh nh tuyn.

Hot ng da trn yu cu: Ti thiu ha phn thng tin iu khin trong

mng, giao thc nh tuyn thuc nhm nh tuyn theo yu cu c th p ng

c iu ny. N ch tm ng khi cn thit v khng qung b thng tin iu

khin lin tc.

Tnh tin phong (proactive): Trong mt s trng hp, tr ln do hot ng da

trn yu cu l khng chp nhn c. Do phi s dng c tnh tin phong

nu ti nguyn ca mng (v mt gii thng) nm trong khong cho php.

H tr cc lin kt mt chiu: Mi trng v tuyn c th l nguyn nhn hnh

thnh cc lin kt theo mt hng. S dng kiu lin kt ny v kiu lin kt hai

chiu s nng cao hiu nng ca giao thc nh tuyn.



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Bo mt: Mi trng v tuyn rt d b tn cng, khai thc thng tin, do m

ha v chng thc l cch bo mt thng thng nht c p dng hin

nay.Vn l vic phn b cc kha v cc nt trong mng Ad hoc.

Bo ton nng lng: Nt mng trong mng Ad hoc c th l my tnh xch tay

hay loi client nh gn khc nh PDA thng c gii hn v thi gian s dng

ca pin, nn cn c ch ch (standby mode) tit kim nng lng. Do ,

giao thc nh tuyn s dng cn h tr ch ch ca nt mng.

Nhiu ng nh tuyn: Nhm gim s ln tc ng do s thay i v cu trc

mng v khi nhiu ng nh tuyn b nghn. Nu nh mt ng nh tuyn

khng s dng c na th mt ng nh tuyn khc c th thay th. Nhvy, giao thc khng cn khi to li th tc tm ng.

H tr QoS: C nhiu loi QoS cn c s h tr ca cc giao thc nh tuyn,

n ph thuc vo mc ch ca mng; chng hn, h tr lu lng thi gian

thc...

2.2.2 Phn loi

so sch v phn tch cc giao thc nh tuyn cho mng Ad hoc, cc phng

thc phn loi hp l l rt quan trng. Cc phng thc phn loi gip cho cc nh

nghin cu v cc nh thit k hiu c nhng c trng khc nhau v mi quan h

gia cc giao thc. Cc c trng ny ch yu lin quan n vic tp hp thng tin

nh tuyn, n vai tr m mt nt c th m nhn trong qu trnh nh tuyn.

2.2.2.1 nh tuyn theo bng, nh tuyn theo yu cu v nh tuyn lai

Mt trong nhng phng thc ph bin nht phn loi cc giao thc nh

tuyn cho mang Ad hoc l da trn vic thng tin nh tuyn c tp hp v c duy

tr nh th no bi cc nt di ng. S dng phng thc ny, cc giao thc nh tuyn

cho mnh Ad hoc c phn chia nh bng 2.2.



24/79


Hnh 2.2 Phn loi cc giao thc nh tuyn trong mng Ad hoc

Cc giao thc nh tuyn proactive: cn c gi l cc giao thc nh tuyn

theo bng (table-driven). S dng cc giao thc ny, cc nt di ng c gng

nh gi lin tc cc tuyn trong mng khi mt gi cn phi chuyn tip

th tuyn sn sng s dng. Mi nt duy tr mt hay nhiu bng

cha thng tin nh tuyn ti cc nt trong mng. Tt c cc nt trong mng

s cp nht cc bng ny duy tr mt cch ph hp thng tin v tnh trng

ca mng, do tiu nh tuyn trong cc giao thc ny l kh ln. Khi

topo mng thay i, cc nt truyn cc bn tin thng bo cho nhau cp

nht thng tin v tuyn ca ton b mng.Giao thc nh tuyn trng thilin kt ti u OLSR (Optimized Link State Routing) v giao thc nh

tuyn vector khong cch tun t ch DSDV (Dynamic Destination-

Sequenced Distance-Vector Routing) l hai v d ca giao thc nh tuynproactive

Cc giao thc nh tuyn reactive: cn c gi l cc giao thc nh tuyn

theo yu cu (on-demand). S dng cc giao thc ny, th tc xc nh

tuyn ch c gi theo yu cu. Vic ny c thc hin thng qua hot



25/79


ng khm ph tuyn ng (route discovery). Qu trnh khm ph tuyn

kt thc sau khi hoc c mt tuyn c tm ra hoc khng c tuyn no sn

c sau khi kim tra ton b cc tuyn ng. Trong mng Ad hoc, cc

tuyn ang hot ng c th b t do tnh di ng ca nt. Do , duy trtuyn l mt hot ng quan trng ca nh tuyn theo yu cu. So snh vi

nh tuyn theo bng, t tiu nh tuyn l 1 u im ca nh tuyn theo

yu cu. Tuy nhin, s dng nh tuyn theo yu cu th vic gi gi tin s

c tr ln do nt ngun phi tm ng trc khi gi d liu. Hai giao thc

reactive in hnh l giao thc nh tuyn vector khong cch theo yu cu

AODV (Ad hoc On-demand Distance Vector Routing) v giao thc nh

tuyn nh tuyn ngun ng DSR (Dynamic Source Routing). Cc giao thc nh tuyn lai (hybrid) c xut kt hp u im ca 2

loi giao thc trn v khc phc cc nhc im ca chng. Thng thng,

cc giao thc lai c trin khai trong mng c cu trc phn cp. Khi ,

cc c tnh nh tuyn theo bng v nh tuyn theo yu cu s c khai

thc c lp cc mc phn cp khc nhau. Zone Routing Protocol (ZRP)

v Hybrid Ad Hoc Routing Protocol l nhng v d ca giao thc lai.

2.2.2.2 Cu trc v phn b tin trnh nh tuyn

Mt phng thc phn loi khc l da trn vai tr c th c ca nt trong c ch

nh tuyn. Trong giao thc nh tuyn ng b, tt c cc nt di ng c cng vai tr

v chc nng. WRP, DSR, AODV v DSDV l nhng v d v nh tuyn ng b.

Cc giao thc ny thng gi nh rng cu trc mng l phng. Trong mt giao thc

nh tuyn bt ng b, mt s nt m nhn vai tr qun l v chc nng khc nhau.

Thut ton phn tn c s dng la chn cc nt c bit ny. Trong mt strng hp, cc phng php nh tuyn bt ng b gn lin vi cu trc mng phn

cp d dng t chc v qun l cc nt. Cc giao thc nh tuyn bt ng b c th

c phn chia da trn vic t chc cc nt di ng, chc nng nh tuyn v qun l

c thc hin nh th no. Theo , cc giao thc nh tuyn bt ng b trong mng



26/79


Ad hoc c chia thnh nh tuyn phn cp theo vng, nh tuyn phn cp theo

nhm v nh tuyn theo nt li.

Trong cc giao thc nh tuyn theo vng, cc thut ton xy dng vng khc

nhau c trin khai cho vic t chc nt; v d, mt s thut ton xy dng vng sdng thng tin v tr a l. Khai thc hiu qu vic phn chia vng s gim c ng

k tiu duy tr thng tin nh tuyn. Cc nt di ng trong cng mt vng bit

ng n cc nt khc s c chi ph nh hn so vi vic duy tr thng tin nh tuyn

ti tt c cc nt trong ton mng. Mt s nt hot ng nh l gateway v m nhn

truyn thng lin vng. ZRP v ZHLS l hai giao thc nh tuyn theo vng cho mng

Ad hoc.

Cc giao thc nh tuyn theo nhm s dng thut ton xy dng nhm cho vicbu chn trng nhm (cluster-head). Cc nt di ng c nhm thnh cc nhm,

trng nhm ng vai tr qun l thnh vin v m nhn chc nng nh tuyn.

Clusterhead Gateway Switch Routing (CGSR) l mt v d ca nh tuyn theo nhm.

Trong cc giao thc nh tuyn theo nt li, cc nt c bit c t ng la

chn gp thnh 1 backbone trong mng. Cc nt backbone m nhn cc vai tr

c bit, nh l xy dng v theo di ng nh tuyn, qung b gi tin d liu. Core-

Extraction Distributed Ad Hoc Routing (CEDAR) l mt v d in hnh ca loi nhtuyn ny.

2.2.2.3 Khai thc cc metric mng cho nh tuyn

Cc metric s dng cho vic xy dng tuyn ng c th c s dng phn

loi cc giao thc nh tuyn trong mng Ad hoc. Gn nh mi giao thc nh tuyn

cho mng Ad hoc s dng s chng lm metric. Nu c nhiu tuyn ng c sn,

tuyn no c s chng nh nht s c la chn. Nu tt c cc lin kt khng dy ccng xc sut li th ng nh tuyn ngn s n nh hn ng nh tuyn di v c

th gim tiu lu lng, gim xung t gi tin. Tuy nhin, gi nh c cng xc sut

li c th khng tn ti trong mng Ad hoc. Theo , s n nh lin kt phi c cn

nhc trong pha xy dng tuyn ng. Vi d, Associatively Based Routing (ARB) v



27/79


Signal-Based Routing (SSR) c xut s dng s n nh lin kt v mnh

tn hiu nh l mt metric cho nh tuyn.

Vi s ph bin ca in ton di ng, mt s ng dng di ng c th c cc yu

cu QoS khc nhau. p ng cc yu cu ny, cc metric QoS tng ng ln cs dng cho vic nh tuyn v chuyn tip gi tin trong mng Ad hoc. Ging nh

mng c dy, cc giao thc nh tuyn QoS cho mng Ad hoc c th s dng cc

metric, nh l bng thng, tr, tr jitter, t l li gi tin v chi ph. V d, bng thng v

n nh lin kt c s dng trong CEDAR lm metric cho vic xy dng tuyn

ng.

2.2.2.4 c lng topo, ch, v tr cho nh tuyn

Trong mt giao thc nh tuyn theo topo cho mng Ad hoc, cc nt tp hp

thng tin topo mng cho vic nh tuyn. Ngoi cc giao thc nh tuyn theo topo,

mt s giao thc nh tuyn theo ch c xut cho mng Ad hoc. Trong cc giao

thc ny, mt nt ch cn bit next-hop trn ng nh tuyn khi chuyn tip gi tin

ti ch. V d, DSR l giao thc nh tuyn theo topo v AODV, DSDV l giao thc

nh tuyn theo ch. Vic sn c ca h thng nh v ton cu (GPS) hoc cc h

thng nh v tng ng cho php cc nt di ng truy nhp thng tin v tr a l

mt cch d dng. Trong cc giao thc nh tuyn theo v tr, mi quan h v v tr gia

cc nt chuyn tip gi tin v nt ch, cng vi s di chuyn ca nt, c th c s

dng trong c qu trnh khm ph tuyn v chuyn tip gi tin. Location Aided

Routing (LAR) v Distance Routing Effect Algorithm for Mobility (DREAM) l cc

giao thc nh tuyn theo v tr cho mng Ad hoc.

Sau y l mt s giao thc nh tuyn c xut cho mng Ad hoc.

2.3 OPTIMIZED LINK STATE ROUTING(OLSR)

OLSR l giao thc nh tuyn theo bng v l mt s ti u ca giao thc trng

thi lin kt c in, hon ton thch hp cho mng di ng Ad hoc. OLSR ti thiu

ha tiu nh tuyn bng cch ch s dng cc nt c chn pht trn lan lu



28/79


lng iu khin, c gi l Chuyn tip a im MPR (Multipoint Relay). K thut

ny gim ng k s lng yu cu truyn li pht trn lan mt bn tin ti tt c cc

nt trong mng.

2.3.1 Bu chn Multipoint relay

Hnh 2.3 Qu trnh pht trn lan bn tin qung b

MPR l ti thiu ha overhead khi pht trn lan bn tin trong mng bng cch

gim s ln truyn li trong cng mt vng. Mi nt trong mng la chn mt tp hp

cc nt hng xm trc tip ca n lm MPR. Hng xm ca nt A m khng nm

trong tp hp MPR ca A c th nhn v x l cc bn tin qung b nhng khng th

truyn cc bn tin qung b nhn c t A.

Mi nt la chn tp hp MPR tnhng hng xm trc tip (one-hop) ca n.

Tp hp MPR ca nt A, k hiu l MPR(A), l tp con ca tp hp cc hng xm trc

tip ca A, phi tha mn nhng iu kin sau: mi nt trong hng xm hai bc (two-

hop) ca A phi c mt lin kt trc tip n MPR(A). Tp hp MPR cng nh th tiu

lu lng iu khin ca giao thc nh tuyn cng nh. Mi nt phi duy tr thng

tin v tp hp hng xm m chng chn lm MPR. Tp hp ny gi l MPR selector

set ca mt nt.



29/79


Hnh 2.4 Bu chn MPR

Trong OLSR, mi nt truyn bn tin Hello nh k (v d mt giy mt bn tin)

trn mi giao din ca nt. Mc ch chnh ca bn tin Hello cho php mi nt c th

khm ph tuyn trc tip ti hng xm ca n. Bn tin Hello c qung b tng

chng mt (hop-by-hop) v phi khng c truyn trc . Bn tin Hello bao gm

tn ca nt khi to, hng xm trc tip m nt khi to truyn bn tin khm ph, v

cc nt m nt khi to chn lm MPRs. Khi mt nt nghe thy bn tin Hello, n kim

tra liu bn tin c phi c pht sinh t hng xm mi hay khng, v nu ng,

nt s cp nht vo danh sch hng xm trc tip ca nt. Bn tin Hello rt quan trng

trong vic h tr khi nim MPR. Mi nt kim tra bn tin Hello nhn c t hng

xm ca n xem n liu c c la chn lm MPR ca bt k hng xm no

khng. Nu vy, nt s pht trn lan cc cp nht nh tuyn c pht sinh t cc

hng xm m chn n l MPR. Mi nt cng c th khm ph liu cc nt c l

hng xm hai bc t bn tin Hello, bi v danh sch cc hng xm hai bc c

lit k trong bn tin Hello ca nt hng xm trc tip ca n. Mi nt la chn MPR

trn c s hng xm hai bc, do vy mi hng xm hai bc phi nhn c bn tin

MPR.



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2.3.2 Truyn b bn tin iu khin topo (Topology control)

Bn tin iu khin topo c truyn i vi mc ch cung cp cho mi nt trong

mng cc thng tin lin kt trng thi y cho php tnh ton c tuyn ng.

2.3.3 Tnh ton tuyn

Thng tin trng thi lin kt a ra c thc hin thng qua trao i nh k cc

bn tin, cng ging nh cu hnh giao din ca cc nt, bng nh tuyn ca mi nt c

th c tnh ton.

2.4 DYNAMIC SOURCE ROUTING (DSR)

Giao thc nh tuyn ngun ng DSR l giao thc nh tuyn n gin v hiu qu.

Giao thc ny c thit k s dng trong cc mng Ad hoc v tuyn a chng c

tc di chuyn cao ca cc nt. Cc nt ny phi hp vi nhau chuyn tip cc gi

tin. Do vy gi tin c th c chuyn n cc nt khng nm trong vng ph sng ca

chnh nt . Khi cc nt trong mng di chuyn, tham gia hoc ri khi mng th ton

b cc th tc nh tuyn c xc nh v duy tr mt cch t ng bi giao thc nh

tuyn DSR.

DSR bao gm 2 c ch c bn: Khm ph tuyn (Route Discovery) v Duy tr tuyn

(Route Maintenance). Khm ph tuyn v Duy tr tuyn hot ng hon ton theo yu

cu.

2.4.1 nh tuyn ngun

DSR pht hin v s dng cc tuyn ngun. Nt gi tin s phi nm c ton b

thng tin v trnh t sp xp ca cc chng (v tr cc nt) ca mng ti mt nt ch.

Mi gi tin c nh tuyn s mang thng tin v danh sch cc chng ny trong tiu. u im quan trng ca th tc nh tuyn ngun l cc nt trung gian khng cn

phi duy tr vic cp nht thng tin nh tuyn khi chuyn tip cc gi tin bi v bn

thn cc gi mang thng tin quyt nh vic nh tuyn (danh sch y cc nt

theo trnh t m gi phi i qua).



31/79


Vic tp hp thng tin v topo mng ti nt ngun ca mi gi cho php nt

ngun phn pht cc gi tin mt cch hiu qu trong mng. iu ny rt thch hp vi

vic qun l ti nguyn trong mng Ad hoc.

Giao thc nh tuyn da trn cc tuyn ngun cn c thm 2 li ch. Th nht,giao thc c th chng minh c mt cch n gin tnh khng lp vng bi v tuyn

ngun c s dng iu khin nh tuyn cc gi. Th hai, mi tuyn ngun l

mt bn k sn v mt ng truyn c th, tin cy truyn cc thng tin qua mng.

DSR s dng cc tuyn ngun v mi gi c nh tuyn da trn mt tuyn

ngun khm ph c, tuy nhin nhng ci thin gn y i vi DSR cho php

hu ht cc gi tin khng phi mang theo phn tiu cha thng tin y v tuyn

ngun.

2.4.2 Khm ph tuyn

Khm ph tuyn c thc hin bng cch pht trn lan yu cu qua mng tm

kim mt tuyn ti ch no . Trong dng n gin nht, nt ngun A mun khm

ph mt tuyn ti nt ch D th A s pht qung b gi tin Yu cu tuyn RREQ v

gi ny tip tc c qung b bi cc nt trung gian cho n khi n n c nt ch

D. Trong c ch ny, nhiu ti u ha c s dng gii hn tn s v phm vi cacc Khm ph tuyn.

Khi mt nt S mun gi mt gi tin n D, u tin n s t vo phn tiu

ca gi tin mt tuyn ngun trong ch ra th t ca cc chng m gi tin s phi

i qua. Thng thng, nt S s t c mt tuyn ngun thch hp thng qua vic tm

kim trong B nh tuyn ca n cc tuyn bit trc y. Tuy nhin nu khng tm

thy tuyn no trong B nh tuyn, n s khi to th tc Tm kim tuyn ng tm

ra mt tuyn ngun ti D. Trong trng hp ny ta gi nt S l nt ngun cn nt D l

nt ch trong th tc Khm ph tuyn.

Trc khi khi to mt gi tin RREQ, nt ngun chn mt nhn dng yu cu

(Request_id) t trong gi tin RREQ. Cp l

duy nht.



32/79


^ "A" ^ "A,B" ^ "A,B,C" ^ "A,B,C,D"| id=2 | id=2 | id=2 | id=2

+-----+ +-----+ +-----+ +-----+ +-----+

| A |---->| B |---->| C |---->| D |---->| E |

+-----+ +-----+ +-----+ +-----+ +-----+

| | | |

v v v v

Hnh 2.5 Khm ph tuyn trong DSR

Hnh 2.5 minh ha qu trnh Khm ph tuyn n gin, nt A c gng khm ph

tuyn ti nt E. khi u Khm ph tuyn, A truyn mt tin bo RREQ. Mi tin

bo RREQ nhn dng nt ngun v ch ca Khm ph tuyn. Nhn dng yu cu

c xc nh bi nt ngun ca Yu cu. Mt RREQ bao gm mt bn ghi danh sch

a ch ca tng nt trung gian m tin bo RREQ i qua. Gi tr ban u ca bn ghituyn l mt danh sch trng.

Khi mt nt nhn c bn tin RREQ ny (v d nh nt B trong v d), nu n l

ch ca Khm ph tuyn, n s gi li bn tin Tr li tuyn RREP ti khi to ca

Khm ph tuyn, chuyn bn copy ca bn ghi tuyn c cng dn t RREQ; khi nt

ngun nhn c RREP, n ct gi tuyn ny trong B nh tuyn s dng khi gi

cc gi tin tip theo ti ch ny.

Mt khc, nu mt nt nhn RREQ m nhn c mt bn tin RREQ khc tnt ngun, mang theo nhng nhn dng yu cu v a ch ch ging nhau hoc nu

a ch ring ca nt ny nm trong bo co tuyn ca RREQ, n s t chi Yu

cu. Nu khng, nt ny s gn a ch ring ca n vo bn ghi tuyn trong bn tin

RREQ v tip tc qung b n. Trong v d, nt B s qung b bn tin RREQ, n s

c nhn nt C, nt C v nt D cng vy, n s broadcast Yu cu, kt qu l copy

ca Yu cu s c nhn bi nt E.

Trong vic bn tin RREP tr li nt ngun trong th tc Khm ph tuyn, chng

hn nt E tr li nt A trong hnh 2.5, nt E s kim tra B nh tuyn ca n xem liu

c mt tuyn ngc v nt A, v nu tm c n s s dng tuyn ny lm tuyn

ngun phn pht cc gi tin bao gm c gi RREP. Nu khng tm c mt tuyn

ngc tr li A, E c th thc hin th tc Khm ph tuyn t n ti A. trnh kh



33/79


nng quay li v hn c th ca cc Khm ph tuyn, n s chn bn tin RREP vo

chnh bn tin RREQ ca n i vi nt A. S dng c ch ny n cng c kh nng

cng theo cc gi d liu nh khc v d nh gi TCP SYN trn mt bn tin RREQ.

Nt E cn c th o v tr sp xp ca cc chng trong bn ghi tuyn v s dng tuyn o v tr ny nh mt tuyn ngun i vi cc gi tin mang bn tin RREP ca

chnh n.

Khi khi to mt Khm ph tuyn, nt ang gi s gi li bn sao ca gi tin ban

u trong b nh m ni b (Send Buffer) gi l b m gi. Ngoi ra Send Buffer

cn cha cc bn sao ca cc gi tin khng truyn i c do cha tm ra mt tuyn

ngun ti ch. Mi gi trong Send Buffer c gn cho mt nhn thi gian ch ra thi

gian chng tn ti trong Buffer v gi tin s b loi b sau khi thi gian lu li trongSend Buffer qu hn; Send Buffer khng b trn, k thut FIFO hoc k thut tng

ng khc c th c s dng truyn cc gi tin i trc khi chng ht hn.

Trong trng hp gi tin cn lu li trong Send Buffer m cha truyn i c

th thnh thong nt mng li thit lp mi th tc Khm ph tuyn ty theo a ch

ch ca cc gi. Tuy nhin, tn sut khi to cc Khm ph tuyn mi cn phi c

gii hn do c th xy ra trng hp ch ca th tc khi to tuyn thay i v

khng th ti c. Trn thc t, do gii hn v phm vi truyn dn v tuyn v s dichuyn ca cc nt trong mng nn nhiu khi cu trc mng b phn mnh, ngha l

khng c th t sp xp ca cc chng m qua gi tin c chuyn tip ti ch.

Kiu phn mnh nh vy c th him gp hoc ph bin ty thuc vo kiu di chuyn

v mt ca cc nt trong mng.

Trong trng hp vi mi gi tin, mt th tc Khm ph tuyn c khi to th

mt s ln cc gi RREQ khng hu ch c truyn t nt ny ti tt c cc nt khc

trong mng. gim phn ph tri tiu do cc Khm ph tuyn trn ngi ta phi

gii hn tn sut khi to cc Khm ph tuyn t mt nt bt k n cng mt ch.

Nt ch c php khi to Khm ph tuyn mi sau khi i ht khong thi gian ti

thiu cn thit c th thit lp th tc Khm ph tuyn mi.



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T kt qu ca vic kim tra bn sao cc tuyn ngun ghi c, thut ton Khm

ph tuyn ngn chn c vic lp cc RREQ trong mng. l mt thuc tnh

hiu chnh quan trng v l nguyn nhn to ra thuc tnh khng lp vng ca DSR. S

dng cc nhn dng yu cu l mt ti u n gin khi cc RREQ ban u tri rnghng ra pha ngoi so vi nt ngun v rt bt s cc gi RREQ bao quanh b khi

to.

2.4.3 Duy tr tuyn

Khi gi hoc chuyn tip mt gi tin ti ch D no s dng tuyn ngun, mi

nt s c nhim v gim st v khng nh rng gi tin n c chng tip theo

trn tuyn ngun hay cha; gi tin s c truyn li (sau mt s ln cho php) cho tikhi nt ny nhn c khng nh rng n n c nt tip theo.V d trng hp

c minh ha trong hnh 2.6 di y: nt A gi mt gi tin ti E s dng mt tuyn

ngun thng qua cc nt trung gian B, C v D. Trong trng hp ny nt A chu trch

nhim v vic nhn gi tin nt B, nt B chu trch nhim vic nhn gi tin nt C,

nt C li chu trch nhim v vic nhn gi tin nt D, v c nh th n nt cui

cng nt D phi chu trch nhim v vic nhn gi tin nt E. Trong nhiu trng hp

khng nh vic nhn gi tin khng nh hng g i vi giao thc DSR do thc t yl mt phn ca cc th tc lp MAC.

Hnh 2.6 Duy tr tuyn, nt C khng th chuyn tip t A n E qualin kt ti bc nhy tip theo D ca n



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Nu c ch ny khng tn ti v sn c cc nt th khi nt gi tin s dng

mt bt thng tin trong phn tiu ca gi tin yu cu mt phc p t nt tip

theo thng qua phn mm c bit trong DSR. Thng thng phc p qua phn mm

ny c truyn trc tip ti nt gi tin. Tuy nhin nu ng lin kt gia hai nt l

lin kt n hng th phc p ny c th phi i qua rt nhiu chng khc nhau

quay li nt gi tin

Nu gi tin c truyn li qua mt s chng v vt qu s ln cc i cho php

m vn cha nhn c khng nh t nt tip theo, nt ny s gi bn tin bo li

tuyn RERR quay tr li nt gi bn tin ban u xc minh tuyn b li t nt

no. V d trong hnh 2.6 trn : nu nt C khng th truyn tin n nt D tip theo, C s

gi bn tin RERR v nt A v tng trnh rng tuyn t C n D b t. Khi A s

xa ng lin kt b li ny khi b nh tuyn ca n. Vic truyn li bn tin ban u

by gi l nhim v v chc nng ca cc th tc lp cao hn nh TCP. Trong trng

hp phi gi li gi tin ti chnh ch E v nu trong b nh tuyn ca nt A c mt

tuyn khc ti E (v d t cc bn tin tr li tuyn t cc th tc khm ph tuyn trc

hoc l t vic nghe lm c cc thng tin nh tuyn t cc gi tin khc) th n s

gi ngay gi tin s dng tuyn mi . Nu khng n s thc hin mt th tc khm

ph tuyn mi ti ch E ni trn

2.5 AD HOC ON- DEMAND DISTANCE VECTOR ROUTING

(AODV)

AODV cho php nh tuyn nhiu bc gia cc nt mng thit lp v duy tr

mng Ad hoc. AODV da trn thut ton vector khong cch nhng thuc loi nh

tuyn theo yu cu, n ch yu cu ng nh tuyn khi cn thit. Thut ton nh

tuyn AODV kh ph hp cho cu hnh mng ng. AODV a ra cc tuyn khng b

lp ngay c khi n ang sa cc lin kt li. Bi v giao thc ny khng yu cu qung

b tuyn nh k trn ton mng, nn yu cu ton b bng thng c sn cho mt nt



36/79


di ng thc cht l thp hn so vi cc giao thc khc, nhng giao thc yu cu

qung b.

AODV s dng lin kt i xng gia cc hng xm. Gi tin khng i theo tuyn

ng gia cc nt khi mt trong nhng nt khng nghe c t cc nt khc.Nhng nt khng nm trn cc tuyn ng hot ng; chng s khng duy tr bt c

thng tin nh tuyn no cng nh khng tham gia vo bt k s trao i bng nh

tuyn nh k no. Hn na, mt nt khng phi khm ph v duy tr mt tuyn ti nt

khc cho ti khi hai nt cn giao tip vi nhau, tr khi nt ng vai tr nh mt

trm chuyn tip trung gian duy tr kt ni gia hai nt khc . Khi mt kt ni cc

b ca nt di ng c thit lp, mi nt c th nhn thy cc nt khc trong vng ln

cn ca n bng mt vi k thut, bao gm qung b cc b cc bn tin Hello. Bngnh tuyn ca cc nt trong vng ln cn c to ra ti u thi gian p ng ti

vi s di chuyn cc b v cung cp thi gian p ng nhanh cho cc yu cu thit lp

tuyn mi.

Mc tiu chnh ca thut ton AODV:

Gi broadcast cc gi tin khm ph tuyn khi cn thit.

Phn bit gia pht hin-qun l kt ni cc b trong vng ln cn vi duy tr

topo mng chung.

Qung b thng tin v s thay i kt ni cc b ti cc nt hng xm m thc

s cn thng tin.

AODV s dng mt c ch Khm ph tuyn vi s ci bin ca thut ton DSR.

Thay v nh tuyn ngun, AODV tin tng vo s thit lp ng cc entry trong Bng

nh tuyn cc nt trung gian.AODV s dng s th t nt mng ch gip cho tuyn ng lun cp nht

v khng hnh thnh ng nh tuyn khp kn. Hn na, AODV cng h tr nh

tuyn multicast v gii quyt c vn m v hn trong thut ton Bellman Ford.



37/79


2.5.1 Khm ph tuyn

Qu trnh Khm ph tuyn c khi to bt c khi no mt nt ngun mun giao

tip vi cc nt mng khc nhng n li khng c thng tin nh tuyn trong Bng

nh tuyn ca n. Mi nt duy tr hai b m: s th t nt v broadcast ID. Ntngun khi to Khm ph tuyn bng cch qung b gi tin RREQ ti hng xm ca

n.

RREQ cha cc trng sau:

Trong :

- source _addr: a ch ngun

- source sequence: s th t ngun

- broadcast_id: nh danh ca RREQ

- dest_addr: a ch ch

- dest sequence: s th t ch

- hop_cnt : s chng

Cp c xc nh duy nht vi mi bn tin RREQ.

broadcast_id c tng ln khi nt ngun khi to mt RREQ mi. Mi nt hng xm

khi nhn c bn tin RREQ s gi li mt bn tin RREP ti nt ngun nu n bit

mt tuyn ti ch, hoc tip tc qung b bn tin RREQ ti nt hng xm sau khi tng

hop_cnt. Ch rng mi nt c th nhn c nhiu bn sao ca cng mt RREQ t

cc hng xm. Khi mt nt trung gian nhn c mt RREQ, nu n nhn RREQ

vi cng broadcast_id v a ch ch, n s loi b RREQ v khng chuyn tip

gi tin na. Nu mt nt khng th p ng c RREQ, n s theo di cc thng

tin sau thit lp tuyn ng ngc cng nh thit lp tuyn ng thun dnh

cho vic truyn gi tin RREP.

a ch IP ch

a ch IP ngun



38/79


Broadcast ID

Thi gian ht hn ca entry tuyn ng ngc

S th t ca nt ngun

2.5.2 Thit lp tuyn ng ngc

C hai s th t c cha trong mt bn tin RREQ: s th t ngun v s th t

ch cui cng c bit bi ngun. S th t ngun c s dng duy tr thng tin

mi v tuyn ng ngc ti ngun, v s th t ch ch ra rng tuyn ng ti

ch phi mi nh th no n c th c chp nhn bi ngun. Khi bn tin RREQ

c gi t nt ngun ti cc nt ch khc nhau, n s t ng thit lp cc tuynng ngc t tt c cc nt ti nt ngun. thit lp tuyn ng ngc, mi

nt phi ghi li a ch ca hng xm m t n nhn c bn sao u tin ca

RREQ. Cc entry tuyn ng ngc c duy tr trong khong thi gian va

bn tin RREQ c th truyn trn mng v tr li li ti nt gi.

Hnh 2.7 Thit lp tuyn ng i ngc



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2.5.3 Thit lp tuyn ng thun

Cui cng, bn tin RREQ s n c mt nt bit c tuyn ti nt ch. u

tin, nt nhn c bn tin RREQ s kim tra chc chn rng bn tin RREQ

c nhn trn mt lin kt hai chiu. Nu mt nt trung gian c mt entry tuyn tich yu cu, n so snh s th t ch trong entry tuyn ca chnh n vi s th t

ch trong bn tin RREQ xc nh xem tuyn c dng c hay khng. Nu s

th t ch trong bn tin RREQ ln hn, nt trung gian s khng s dng tuyn trong

bng entry tuyn ca n p ng RREQ. Khi , nt trung gian s tip tc qung b

RREQ. Cc nt trung gian ch tr li khi s th t ch trong bng entry ca n ln hn

so vi trong bn tin RREQ. Nu nt trung gian c mt tuyn hin hnh ti nt ch v

nu bn tin RREQ ny cha c nhn trc , nt s gi unicast mt bn tin RREP

ti hng xm m t n nhn c RREQ.

Mt bn tin RREP cha cc thng tin sau:

Trong khi mt gi tin qung b ti mt nt c tuyn ti ch, mt tuyn ng

ngc c thit lp ti nt ngun ca gi tin RREQ. Khi RREP tr li nt ngun, mi

nt dc theo tuyn ng thit lp mt con tr thun ti nt m t RREP n, cp

nht thng tin timeout cho cc entry ti nt ngun v nt ch, ghi li s th t ch

mi nht cho tuyn c yu cu. Thit lp tuyn ng thun khi RREP t nt ch D

ti nt ngun S. Nt khng nm trn tuyn c xc nh bi RREP s ht hn sau

ACTIVE_ROUTE_TIMEOUT (3000ms) v s xa con tr ngc.

Mt nt nhn RREP s truyn RREP u tin v nt ngun. Nu mt nt nhn

nhiu hn mt RREP, n s cp nht thng tin nh tuyn ca n v truyn RREP ch

khi RREP c s th t ch ln hn hoc bng RREP trc vi mt s chng nh

hn. N s loi b ht cc RREP khc m n nhn c. iu ny gim s lng bn

tin RREP truyn ti nt ngun ng thi m bo rng thng tin nh tuyn l nhanh

v mi nht. Nt ngun c th truyn d liu ngay sau khi nhn c RREP u tin

v sau c th cp nht thng tin nh tuyn nu n hc c mt tuyn mi tt hn.



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Hnh 2. 8 Thit lp tuyn ng thun

2.5.4 Qun l bng nh tuyn

Gn lin vi cc entry tuyn ng ngc l mt b m thi gian, c gi l

b m thi gian ht hn RREQ. Mc ch ca b m thi gian ny l thanh lc

nhng entry tuyn ng ngc t nhng nt khng nm trn tuyn ng t ngun

ti ch.

Thi gian ht hn ph thuc vo kch thc ca mng Ad hoc. Mt thng s quan

trng khc gn vi entry nh tuyn l thi gian timeout ca cc tuyn ang c lu

gi, hay thi gian m sau tuyn ng ny coi nh ht hiu lc. Trong mi entry

Bng nh tuyn, a ch ca nt hng xm m gi tin i qua n ch cng c

duy tr. Mt nt c coi l hot ng i vi ch khi n to ra hay chuyn tip t

nht mt gi tin ti ch trong khong thi gian timeout . Thng tin ny c duy

tr tt c cc nt ngun c th c thng bo khi c mt lin kt b t. Mi nt

duy tr mt entry cho mi ch cn n. Mi entry cha cc thng tin sau:

- ch



41/79


- Next hop

- S chng

- S th t ch

- Cc hng xm cn hot ng cho ch - Thi gian ht hn cho entry bng nh tuyn

Mi khi mt entry tuyn c dng truyn gi tin d liu t ngun ti ch,

timeout cho entry s c reset ti thi gian hin ti cng thm timeout. Nu mt

tuyn mi c yu cu cho mt nt di ng, cc nt di ng so snh s th t ch

ca tuyn mi vi tuyn hin ti. Nu s th t tuyn mi cao hn, n s c chn,

nu bng nhau th tuyn mi s c chn khi c metric nh hn (s chng t hn) ti

ch.2.5.5 Cp nht ng nh tuyn

Khi mt nt mng pht hin ng nh tuyn n nt bn cnh khng hot ng,

n s xa trong bng nh tuyn v gi mt bn tin Lin kt hng RERR. AODV s

dng danh sch nt mng bn cnh cn hot ng ghi nh nt mng ang s dng

ng nh tuyn trong bng nh tuyn. Nt mng nhn c bn tin ny cng s lp

li qu trnh gi bn tin. Cui cng bn tin cng n c gi n tt c nt mng c

lin quan, t chng c th dng vic gi thng tin hoc yu cu ng nh tuyn

mi thng qua bn tin RREQ.

2.6 DYNAMIC MANET ON- DEMAND (DYMO)

DYMO l giao thc nh tuyn theo bng mi nht, hin vn ang c pht trin

bi MANET trong IETF. DYMO c th coi l s kt hp ca AODV v DSR. Mc

tiu ca n l thit k n gin, gim thiu yu cu h thng , n gin ha vic thcthi giao thc. Mt mt, DYMO cng s dng s th t m bo trnh lp tuyn, mt

khc, DYMO a ra cc c tnh mi nh l thc hin tnh ton tuyn ng. Bn

cnh thng tin tuyn ng v mt mc tiu c yu cu, mt nt cng nhn c

thng tin v tt c cc nt trung gian nm trn mt tuyn ng mi khm ph c.



42/79


y l mt khc bit c bn gia DYMO v AODV, trong th AODV ch to ra

entry bng nh tuyn cho nt ch v nt next-hop, cn DYMO th lu tr tuyn

ng cho mi nt trung gian. iu ny c th hin qua hnh 2.9.

Hnh 2.9: S khc nhau gia AODV v DYMO

Khi s dng AODV, mt nt A ch bit ng ti B v D sau khi Yu cu tuyn

c p ng. Trong DYMO, nt A cng bit c ng ti C. DYMO c th thit lp

v duy tr cc tuyn ng unicast trong cc kch bn mng IPv4 v IPv6 bng cch s

dng c ch sau:

Nhm pht hin mt tuyn mi n mt nt ch, mt nt gi mt bn tin Yu

cu tuyn RREQ ti tt c hng xm trong phm v truyn sng ca n. iu

ny cng nhn c bng cch gi bn tin ti 1 a ch multicast cc b ring.

Khi mt nt trung gian nhn c mt RREQ n thit lp tuyn ng ti tt c

cc nt m gi tin i qua. Sau nt s gn a ch ca chnh n vo bn tin

v truyn bn tin ti tt c cc nt ln cn. Bng cch ny th RREQ c qung

b mt cch hiu qu trn mng v cui cng l n ch ca n.

ich p ng RREQ bng cch gi unicast mt bn tin Tr li RREP tr v nt

m n m t n nhn c RREQ. Cng nh trong qu trnh qung b

RREQ, nt ny li gn a ch ca n v ghi ch tt c cc thng tin nh tuyn

c trong RREP. Cng vi thng tin nh tuyn c c trc khi chuyn



43/79


tip RREQ tng ng, nt trung gian c kh nng gi RREP tr v nt ngun

ca RREQ. Nt ny cng s bit c tuyn ng ti nt ch c yu cu,

cng nh l ng ti mi nt trung gian, v ngc li.

Mt nt trung gian cng c th to ra RREP nu nh n bit tuyn ng ti ch.

phn ng tt vi mng c mc di chuyn cao, cc lin kt trn tuyn ng

bit c c th c theo di, bng cch s dng giao thc nhn bit hng xm

(Neighboehood Discovery Protocol) hoc kim tra phn hi nhn c tng data

link. Mt h thng cng c th la chn khng bt tnh nng theo di, n gin ch xa

cc tuyn khng cn hot ng. Khi mt nt pht hin lin kt li, n s gi mt bn

tin RERR thng bo c tt c cc nt ln cn, thng bo cho chng bit v tt c cc

tuyn t.

TNG KT

Qua vic nghin cu mt s giao thc trong mng Ad hoc ta c th thy rng

cha c giao thc no c y cc tnh nng v khng th khng nh giao thc no

l ti u cho mng Ad hoc. Tuy nhin, chc nng chnh ca cc giao thc l tm c

ng i ti ch, khng phi ng ngn nht hay ng ti u nht c p ng.



44/79


3 CHNG 3 THNG S NH GI V M HNH

CHUYN NG TRONG M PHNG MNG AD

HOC

Nh trnh by chng 2, giao thc nh tuyn trong mng Ad hoc u tptrung gii quyt vn v khi nim c trng ca mi trng v tuyn. Nhng giao

thc no l tt nht, ph hp nht? N ph thuc vo cu trc v thuc tnh ca mng,

mt nt mng, mc di chuyn ca nt mng, kch c mi trng, kiu di chuyn

ca cc nt mng...

3.1 THNG S NH GI GIAO THC MNG AD HOC

C hai thng s nh gi: thng s nh gi cht lng v thng s kch bn.

3.1.1 Thng s nh gi cht lng



45/79


Cc thng s ny c s dng a ra chnh xc nhng g xy ra trong qu

trnh m phng v cung cp cc thng tin c gi tr v cc giao thc nh tuyn. Do ,

n dnh c nhiu s quan tm khi nghin cu giao thc nh tuyn m phng.

3.1.1.1 T l gi nhn c

nh ngha: T l gi nhn c RD l t l gia s gi nhn c bi nt ch

(PR) v s gi c gi i t lp ng dng ca nt ngun (PS).

RD = PR /PS (CT 3.1)

ngha: giao thc nh tuyn hot ng tt phi c gi tr RD cao do kh nng tn

dng bng thng v tuyn l rt quan trng. Thng s ny phn nh t l gi tin b mt,

mc hon chnh v ng n ca giao thc nh tuyn.

3.1.1.2 Tr t u cui n u cui

nh ngha: Tr t u cui n u cui l thi gian m gi tin truyn trn mng

t nt ngun n nt ch. N bao gm nhiu gi tr nh trn mng: tr b m, tr

chuyn tip gi tin nt trung gian, tr truyn dn v thi gian truyn li gi tin

(trong trng hp gi tin b mt). C th tnh thi gian tr theo hai cch:

Tdelay = Trev T send (CT 3.2)

Hoc: Tdelay = T buffer+ Trelay + Tprop + Tresend (CT 3.3)

ngha: Trong mng gi v tuyn khng c QoS th gi tr tr ph thuc vo giao

thc nh tuyn. Mt thng s quan trng l thi gian tr trong b m, tc l gi tin

c lu gi trong b m khi cha c ng nh tuyn n ch trc khi b hy.Nu nh nt mng t thi gian ln th t gi tin trn mng b hy, nhng cng c

ngha tr trung bnh trong mng cng tng ln. V ngi thit k h thng s quyt

nh: t l gi hy b thp hay thi gian tr, iu ny lin quan n gi tr tr u cui

n u cui.



46/79


3.1.1.3 Thng lng t u cui n u cui

nh ngha: thng lng l t l gia s gi tin d liu c truyn trn mt n

v thi gian.

ngha: Khi bng thng sn c trn mng bit, th trong m phng bng thngthc s c c l bao nhiu? Thng s thng lng T s cho bit bng thng thc s

khi m phng v c th cho thy s hiu qu ca giao thc nh tuyn mc no.

Khi thng lng trung bnh cao ngha l bng thng dnh cho nh tuyn l t, khi

giao thc nh tuyn hot ng tt.

3.1.1.4 Phn ti thng tin nh tuyn

nh ngha: l t l gia gi tin nh tuyn c gi i vi s gi d liu c giti ch.

ngha: Ti thng tin nh tuyn l mt thng s quan trng vi mng Ad hoc,

n cng cho bit hiu nng s dng bng thng ca giao thc nh tuyn: bao nhiu

bng thng c s dng cho bn tin nh tuyn, bao nhiu bng thng c s dng

cho cc gi tin d liu. Phn ti nh tuyn trong giao thc nh tuyn theo yu cu

thng thng l ln do n phi gi bn tin cp nht nh k trn ton mng. Trng

hp l tng l khng c bn tin nh tuyn, ch c gi tin d liu c truyn trnmng; tuy nhin, nu khng c giao thc nh tuyn th khng th trin khai thc t.

3.1.2 Thng s kch bn

Cc thng s kch bn c tnh ton t d liu u vo ca m phng, hoc c

th l bin u vo (v d nh thi gian tm dng). N khng ph thuc vo giao thc

nh tuyn hoc qu trnh m phng cng nh cc thng s nh gi cht lng m ta

nghin cu trn. N cung cp s so snh tht nht gia cc giao thc.

3.1.2.1 Thng s di chuyn



47/79


N nh gi s chuyn ng trong mng bng cch tnh ton di chuyn ca nt mng

lin quan gia cc cp nt trn mng. Thng s ny tng ng vi s thay i lin kt

trong m hnh khi m nt mng di chuyn theo m hnh nh trc.

Bng 3.1 Bng cc bin trong thng s di chuyn

Tn

bin

M t

Dist(nx, ny)t Khong cch gia nt X v nt Y thi im tn S nt mngi Ch sAx(t) Khong cch trung bnh gia cc nt x vi cc nt khc thi im t

Mx Di chuyn trung bnh ca nt x vi cc nt trong thi gian m phngT Thi gian m phngt Bc thi gian m phngMod Di chuyn trong ton b kch bn [m/s]

Bc 1: tnh khong cch trung bnh ca cc nt x vi cc nt khc trong mng c

thc hin cc thi im t=0, t= 0 + X, t=0 + 2X, ... t = T, theo cng thc:

(CT 3.4)

Bc 2: Tnh di chuyn ca nt x theo cng thc:

(CT 3.5)

Bc 3: Tnh thng s di chuyn cho c kch bn:

(CT 3.6)

2.4.3.1 Thi gian tm dng

Thi gian tm dng l mt bin u vo ca m phng. Khi s dng nh mt

thng s nh gi, thi gian tm dng ca tt c cc nt trong m phng c s dng



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o kim thng s chuyn ng. Khi gi tr trung bnh cng ln th nt mng cng t

di chuyn trong mng.

3.2 M HNH DI CHUYN M PHNG MNG AD HOCTrong mng Ad hoc, nt mng di chuyn t v tr ny n v tr khc, nn kh

khn khi tm ra m hnh di chuyn c th cho m phng. c th m phng giao thc

nh tuyn th cn phi c s pht trin v s dng m hnh di chuyn cho nt mng,

do vic xc nh m hnh di chuyn l rt quan trng.

M hnh di chuyn yu cu phi m t di chuyn ca nt mng ging nh trong

thc t, cn c s thay i v hng v tc di chuyn trong nhng khong thi gian

hp l. Chc chn nt mng thc khng th di chuyn theo ng thng vi tc

khng i trong sut qu trnh m phng. Vn tc c th thay i v gim n 0, tng

t hng di chuyn cng s thay i.

C rt nhiu m hnh p dng cho mng Ad hoc, c th tng ng vi tng ng

cnh kch bn m phng, trong gii hn n cp mt s m hnh tiu biu.

3.2.1 M hnh di chuyn ngu nhin

M hnh di chuyn ngu nhin l m hnh di chuyn n gin da trn hng vvn tc ngu nhin, trong vn tc v hng hin ti ca hai hay nhiu nt mng

hon ton c lp vi gi tr c ca chng. Do , m hnh s phi i mt vi hin

tng khng ging thc t: dng t ngt, c vng quay nhn, ng di chuyn quanh

co hon ton ngu nhin. khc phc vn ny, ngi ta c th thay i m hnh

bng cch tnh ton vn tc hay hng di chuyn hoc c hai.

3.2.2 M hnh di chuyn hng ngu nhin vi vn tc khng iy l m hnh sa i ca m hnh di chuyn ngu nhin nhng m bo tt c

nt mng c gn cho mt vn tc nh nhau trong sut qu trnh m phng. Sau khi

hng chn mt cch ngu nhin trong khong (0, 2), cc nt bt u di chuyn. Khi



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gp bin ca khu vc m phng, n ny khi bin vi mt gc xc nh bi hng n,

cc nt di chuyn thao ng mi.

3.2.3 M hnh di chuyn Random Waypoint

M hnh ny c s dng thi gian tm dng khi thay i hng v vn tc. Hai

hay nhiu nt mng mt v tr trong mt khong thi gian (thi gian tm dng). Khi

ht thi gian tm dng, nt mng chn ngu nhin vn tc trong khong (0, maxspeed)

Hnh 3.1 M hnh di chuyn Random Waypoint

3.2.4 M hnh di chuyn hng ngu nhin

M hnh ny khc phc nhc im ca m hnh Random Waypoint, do cc nt

trong m hnh Random Waypoint thng chn cc ch mi v xc sut chn thng

l trung tm khu vc m phng hoc ng i qua trung tm khu vc m phng. Khi

cc nt mng c xu hng hi t, phn tn... trong m hnh di chuyn hng ngu



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nhin, cc nt chn hng thay v chn ch, sau n di chuyn theo hng n

bin ca khu vc m phng, ngay khi n bin n dng li trong mt khong thi gian

v chn hng khc (0, 180o) v tip tc qu trnh .

Hnh 3.2 M hnh di chuyn hng ngu nhin

TNG KT

Vic la chn cc thng s nh gi giao thc v m hnh di chuyn l rt quan

trng. Thng qua cc thng s , ta c th nh gi c im mnh cng nh im

yu ca mt giao thc mng. Qua , ta c th la chn c giao thc ph hp cho

nhng gi thit v yu cu t ra.



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4 CHNG 4. M PHNG V NH GI THNG

LNG CA AODV, OLSR, DSR V DYMO BNG

OMNET++

Chng ny s gii thiu v cng c m phng giao thc nh tuyn mang Ad

hc, m phng cc giao thc nh tuyn, gi thit u vo cho qu trnh m phng. Kt

qu m phng v nh gi, kt lun.

4.1 GII THIU CHUNG V OMNET++

4.1.1 Tng quan v Omnet++

4.1.1.1 Omnet ++ l g ?

OMNeT++ l vit tt ca cm t Objective Modular Network Testbed in C++.

OMNeT++ l mt ng dng cung cp cho ngi s dng mi trng tin hnh

m phng hot ng ca mng. Mc ch chnh ca ng dng l m phng hot ng

ca mng thng tin, tuy nhin do tnh ph cp v linh hot ca n, OMNeT++ cn

c s dng trong nhiu lnh vc khc nh m phng cc h thng thng tin phc

tp, cc mng kiu hng i (queing networks) hay cc kin trc phn cng

OMNeT++ cung cp sn cc thnh phn tng ng vi cc m hnh thc t. Cc

thnh phn ny (cn c gi l cc module) c lp trnh theo ngn ng C++, sau

c tp hp li thnh nhng thnh phn hay nhng m hnh ln hn bng mt

ngn ng bc cao (NED). OMNeT++ h tr giao din ha, tng ng vi cc m

hnh cu trc ca n ng thi phn nhn m phng (simulation kernel) v cc module

ca OMNeT++ cng rt d dng nhng vo trong cc ng dng khc.

4.1.1.2 Cc thnh phn chnh ca OMNeT++

Trong OMNeT++ c cc thnh phn chnh sau:



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Th vin phn nhn m phng (simulation kernel)

Trnh bin dch cho ngn ng m t tnh trng (topology description

language) NED (nedc)

Trnh bin tp ha (graphical network editor) cho cc file NED

(GNED)

Giao din ha thc hin m phng, cc lin kt bn trong cc file thc

hin m phng (Tkenv)

Giao din dng thc hin m phng (Cmdenv)

Cng c (giao din ha) v th kt qu vector u ra (Plove)

Cng c (giao din ha) m t kt qu v hng u ra

(Scalars)Cng c ti liu ha cc m hnh

Cc tin ch khc

Cc ti liu hng dn, cc v d m phng

4.1.1.3 ng dng

OMNeT++ l mt cng c m phng cc hot ng mng bng cc

module c thit k hng i tng. OMNeT++ thng c s dng trong cc

ng dng ch yu nh:

M hnh hot ng ca cc mng thng tin

M hnh giao thc

M hnh ha cc mng kiu hng i

M hnh ha cc h thng a b vi x l (multiprocessor) hoc cc h thng

phn cng theo cc m hnh phn tn khc (distributed hardware systems)

nh gi kin trc phn cng

nh gi hiu qu hot ng ca cc h thng phc tp



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4.1.1.4 M hnh trong OMNeT++

Mt m hnh trong OMNeT++ bao gm cc module lng nhau c cu trc phn

cp. su ca cc module lng nhau l khng gii hn, iu ny cho php ngi s

dng c th biu din cc cu trc logic ca cc h thng trong thc t bng cc cutrc m hnh. Cc module trao i thng tin vi nhau thng qua vic gi cc message.

Cc message ny c th c cu trc phc tp ty . Cc module c th gi cc message

ny theo hai cch, mt l gi trc tip ti a ch nhn, hai l gi i theo mt ng

dn c nh sn, thng qua cc cng v cc kt ni.

Cc module c th c cc tham s ca ring n. Cc tham s ny c th c s

dng chnh sa cc thuc tnh ca module v biu din cho topology ca m

hnh.Cc module mc thp nht trong cu trc phn cp ng gi cc thuc tnh. Cc

module ny c coi l cc module n gin, v chng c lp trnh trong ngn ng

C++ bng cch s dng cc th vin m phng.

Mt m hnh trong OMNeT++ cha cc module lng nhau c cu trc phn cp,

trao i thng tin vi nhau bng cch gi cc message. Mi m hnh ny thng biu

din cho mt h thng mng. Module mc cao nht trong cu trc phn cp c gi l

module h thng. Module ny c th cha cc module con, cc module con cng c thcha cc module con ca ring n. su phn cp i vi cc module l khng gii

hn, iu ny cho php ngi s dng c th d dng biu din mt cu trc logic ca

mt h thng trong thc t bng cu trc phn cp ca OMNeT++.

Cu trc ca m hnh c th c m t bng ngn ng NED ca OMNeT++

Hnh 4.1 Cc module n gin v kt hp



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Cc module c th cha nhiu module con v c gi l module kt hp. Cc

module n gin l cc module c cp thp nht trong cu trc phn cp. Cc module

n gin cha cc thut ton ca m hnh. Ngi s dng trin khai cc module n

gin bng ngn ng C++, s dng cc th vin m phng ca OMNeT++.Cc module trao i thng tin bng vic gi cc message. Trong thc t, message

c dng khung (frame) hoc l cc gi tin (packet) c truyn i trong mng. Cc

message c th c cu trc phc tp ty . Cc module n gin c th gi cc

message i mt cch trc tip n v tr nhn hoc gi i theo mt ng dn nh sn

thng qua cc cng (gates) v cc lin kt (links).

Cc cng (gates) l cc cng vo, ra ca cc module. Message c gi i qua

cc cng ra v c nhn vo thng qua cc cng vo.

Mi kt ni (connection) hay cn gi l lin kt (link) c to bn trong mt

mc n trong cu trc phn cp ca cc module: bn trong mt module kt hp, mt

kt ni c th c to ra gia cc cng tng ng ca hai module con, hoc gia cng

ca module con vi cng ca module kt hp.

Hnh 4.2 Cc kt ni

Tng ng vi cu trc phn cp ca mt m hnh, cc message thng di

chuyn qua mt lot cc kt ni vi im bt u v kt thc l cc module n gin.Tp cc kt ni i t mt module n gin v n mt module n gin c gi l

route.



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4.1.2 S dng OMNeT++

4.1.2.1 Xy dng v chy th cc m hnh m phng

a. Mt m hnh OMNeT++ bao gm nhng phn sau Ngn ng m t topology NED (file c phn m rng .ned): m t cu

trc ca module vi cc tham s, cc cng Cc file.ned c th c vit bng bt k

b son tho hoc bt k b son tho hoc s dng chng trnh GNED c trong

OMNeT++

nh ngha cu trc ca cc message (cc file c phn m rng .msg):

Ngi s dng c th nh ngha rt nhiu kiu message v thm cc trng d liu

cho chng. OMNeT++ s dch nhng nh ngha ny sang cc lp C++ y .

M ngun ca cc module n gin. y l cc file C++ vi phn m

rng l .h hoc .cc.

b. H thng m phng cung cp cho ta cc thnh phn sau

Phn nhn m phng. Phn ny cha code qun l qu trnh m phng

v cc th vin lp m phng. N c vit bng C++, c bin dch v c t

cng dng vi cc file th vin (cc file c phn m rng l .a hoc .lib).

Giao din ngi s dng. Giao din ny c s dng khi thc hin qu

trnh m phng, to s d dng cho qu trnh sa li, biu din (demonstration) hoc

khi thc hin m phng theo tng khi (batch execution of simulations). C mt vi

kiu giao din trong OMNeT++, tt c u c vit bng C++, c bin dch v t

cng nhau trong cc th vin (cc file c phn m rng l .a hoc .lib)

c. Thc hin m phng v phn tch kt qu

Cc chng trnh thc hin m phng (the simulation executable) l cc

chng trnh c lp, tc l n c th chy trn cc my khc khng ci t

OMNeT++ hay cc file m hnh tng ng. Khi chng trnh khi ng, n bt

u c file cu hnh (thng thng l file omnetpp.ini). File ny cha cc thit lp



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iu khin nhiu qu trnh m phng, trong trng hp n gin nht l cc qu

trnh m phng ny s c thc hin ln lt bi mt chng trnh m phng

(simulation program).

u ra ca qu trnh m phng l cc file d liu. Cc file ny c th lcc file vector, cc file v hng hoc cc file ca ngi s dng. OMNeT++ cung

cp mt cng c ha Plove xem v v ra ni dung ca cc file vector. Tuy

nhin chng ta cng nn hiu rng kh m c th x l y cc file kt qu m

ch dng ring OMNeT++; cc file ny u l cc file c nh dng c th c

c bi cc gi x l ton hc ca cc chng trnh nh Matlab hay Octave, hoc

c th c a vo tnh ca cc chng trnh nh OpenOffice Calc, Gnumeric hay

Microsoft Excel. Tt c cc chng trnh ny u c chc nng chuyn dng trongvic phn tch s ha, v biu din (visualization) vt qua kh nng ca OMNeT+

+.

Cc file v hng cng c th c biu din bng cc cng c Scalar. N c

th v c cc biu , cc th da vo tp hp cc ta (x,y) v c th xut

d liu vo clipboard c th s dng trong cc chng trnh khc nhm a

nhng phn tch chi tit hn.

d. Giao din ngi s dngMc ch chnh ca giao din ngi s dng l che nhng phn phc tp bn

trong cu trc ca cc m hnh i vi ngi s dng, d dng iu khin qu trnh

m phng, v cho php ngi s dng c kh nng thay i cc bin hay cc i

tng bn trong ca m hnh. iu ny l rt quan trng i vi pha pht trin v

sa li trong d n. Giao din ha cng c th c s dng trnh din hot

ng ca m hnh.

Cng mt m hnh ngi s dng c th trn nhiu giao din khc nhau

m khng cn phi thay i g trong cc file m hnh. Ngi s dng c th kim

th v sa li rt d dng qua giao din ha, cui cng c th chy n da trn

mt giao din n gin v nhanh chng c h tr thc hin theo khi (batch

execution)



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e. Cc th vin thnh phn

Cc kiu module c th c lu ti nhng v tr c lp vi ch m chng

thc s c s dng. c im ny cung cp cho ngi s dng kh nhm cc

kiu module li vi nhau v to ta cc th vin thnh phn.f. Cc chng trnh m phng c lp

Cc chng trnh thc hin qu trnh m phng c th c lu li nhiu ln,

khng ph thuc vo cc m hnh, s dng cng mt thit lp cho cc module n

gin. Ngi s dng c th ch ra trong file cu hnh m hnh no s c chy.

iu ny to kh nng cho ngi s dng c th xy dng nhng chng trnh thc

hin ln bao gm nhiu qu trnh m phng, v phn phi n nh mt cng c m

phng c lp. Kh nng linh hot ca ngn ng m t topology cng h tr chohng tip cn ny.

4.1.2.2 Chy cc ng dng trong OMNeT++

Nh trnh by phn m u, mt h thng mng m phng trong OMNeT++

gm cc thnh phn sau:

Cc file.ned m t topo mng.

Cc file c phn m rng .msg cha khai bo cc message.

Cc file C++ (c phn m rng l .cc trong UNIX hoc .cpp trong

Windows)

Qu trnh xy dng mt chng trnh m phng

u tin, dch cc file NED v cc file message thnh C++, s dng

NED compiler (nedc) v message compiler (opp_msgc).

Qu trnh tip theo ging nh bin dch m ngun C/C++

Trong Linux: cc file .cc file.o.

Trong Windows: cc file .cpp file .obj.



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Sau tt c cc file trn s c lin kt (link) vi cc th vin cn thit

to thnh file .exe.

C th ta cn phi lin kt vi cc th vin sau:

Phn nhn m phng c gi l sim_std (nh cc file libsim_std.a,sim_std.lib, etc)

Giao din ngi dng: cung cp th vin mi trng (file libenvir.a, etc)

v cc tin ch tkenv v cmdenv (libtkenv.a, libcmdenv.a, etc). Cc file .o (hoc .obj)

phi c lin kt ti th vin mi trng cng vi hoc tkenv hoc cmdenv.

Hnh di y cho chng ta hnh nh qu trnh x l khi m hnh c xy dng

v hot ng



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*.ned l cc file m t topo mng cng nh cu trc ca cc modul, n s dng

ngn ng NED (Nework Description ), l ngn ng chuyn bit dng ring cho

OmNet++. S pht trin tip theo ca NED l GNED (Graphic NED) lm cho vic mt topo mng c trc quan hn bng cch dng cc cng c ho m t. Cc

file ned sau c NEDC (NED compiler) dich sang code C++ m t cu trc

mng sang ngn ng C++ di dng file *_.cc.


File m tcu trcmng

*.ned

File x l casimple modules

*.cc

Th vin li cachng trnh mphng *.lib / *.a

Th vin giao dinngi dng*.lib / *.a

File m t cu trcmng sau khi dch

*_n.cc

C++ compiling

Linking

Chng trnh mphng

Chy chngtrnh

File cu hnhOmnetpp.ini

File kt qu*.vec, *.sna, *.sca

NEDC compling

Hnh 4.3 Lc xy dng v chy mt chng trnh m phngOMNeT++


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Cc file x l ca cc simple moduls l phn ct li khi vit chng trnh m

phng v c vit bng ngn ng C++ bng cch k tha cc lp c sn ca OmNet+

+, ngi vit trin khai cc hot ng ca mng nh nh tuyn, x l gi tin n v i,

xc nh hnh vi ca cc simple modul c m t trong *.ned khi c s kin xy ravi n.

Th vin li ca chng trnh m phng c cung cp bi OmNet++, n bao

gm rt nhiu cc lp v cc hm c sn phc v cho chng trnh m phng nh cc

lp cSimplemodul, cMessage..., cc hm ngu nhin Th vin giao din ngi dng

cung cp giao din cho chng trnh m phng. OmNet++ vi cc phin bn gn y

s dng hai kiu giao din l giao din dng lnh cmd (command) v giao din ho

da trn tcl/tk. Giao din ho rt trc quan nn c a dng hn. Sau khi dch vlin kt ta c mt chng trnh m phng da trn nn OmNet++.

File omnetpp.ini khi ng cc gi tr cn thit. omnetpp.ini do ngi lp trnh

vit, n rt quan trng chy mt chng trnh m phng vi cc tham s c thay

i c c kt qu thng k mong mun.

Cui cng l cc file kt qu bao gm file *.vec l cc file vector, n l cc bin

thay i theo thi gian trong qu trnh m phng, gi tr ca bin v thi gian tngng c lu vo file ny. Trong qu trnh vit code s xc nh bin no c lu.

File *.sna phc v cho qu trnh sa li. File *.sca (scalar file) lu cc gi tr thng k

c c sau khi kt thc m phng, v d nh s cuc gi thc hin s cuc gi b t

chi x l kt qu thng k t c, ta c th vit mt chng trnh nh hoc s

dng cc cng c c sn. OmNet++ cung cp chng trnh Plove v cc file *.vec,

cn i vi cc file *.sca ta c th dng mt chng trnh tnh ton bt k.

4.2 M PHNG

4.2.1 Khi to m phng

Trong tt c cc kch bn m phng, n s dng m hnh di chuyn Random

Waypoint vi cc thng s sau:



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Vn tc ti a speedmax: bt k thi im no vn tc c gi tr ngu nhin

trong khong [0, speedmax].

S nt mng: gi tr ny khng thay i trong ton b qu trnh m phng, n

s dng 25 nt mng trong kch bn m phng.

Kch c mi trng m phng: n s dung khu vc m phng 500x500m

cho ton b kch bn m phng.

Thi gian m phng : 300s cho tt c kch bn m phng.

Thi gian tm dng: thay i vi cc gi tr 0, 100, 200, 300.

4.2.2 Mt s hnh nh m phng

Sau y l tun t cc qu trnh ca DYMO: Khm ph tuyn bng cch gi

RREQ, gi bn tin RREP, gi gi tin d liu, v gi ACK bo nhn.



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Trc khi gi gi tin ti mt ch, mt nt s kim tra trong B nh tuyn ca n

c tuyn ti ch hay khng. Nu khng c, n s gi bn tin RREQ Khm phtuyn (hnh 4.4).

Hnh 4.4 Qu trnh gi bn tin RREQ ca DYMO



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Cc nt nhn c bn tin RREQ, nu nt l ch hoc bit mt tuyn ng

ti ch, n s gi li bn tin RREP v ngun (hnh 4.5)

Hnh 4.5 Qu trnh gi bn tin RREP ca DYMO



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Nh vy, nt ngun c mt tuyn ti ch v n thc hin qu trnh gi gi tin

d liu hnh (hnh 4.6).

Hnh 4.6 Qu trnh gi gi tin d liu ca DYMO



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Nt ch nhn c gi tin d liu, n s gi ACK ti nt ngun xc nhn n

nhn c gi t nt ngun (hnh 4.7).

Hnh 4.7 Qu trnh gi ACK bo nhn ca DYMO



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4.2.3 Kt qu m phng cc giao thc nh tuyn mng Ad hoc

Bng 4.1 Bng thng s nh gi dng trong m phng

Thng s Gi tr

Phm vi truyn dn 250mBng thng 54Mbps (802.11g)Thi gian m phng 300sKch thc mi trng m phng 500m x 500mLoi lu lng CBRTc gi gi tin 4 packet/s

Kch thc gi tin 512 bytesS nt 25S ngun gi gi tin 5Tc ti a 20m/s

Kch bn l mt phn rt quan trng trong m phng, y n a ra 4 gi tr

cn o c

45771405-Đồ-an-tốt-nghiệp-Vũ-Huy-Cường

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